1. Field of the Invention
The present invention relates to an endoscope, and in particular, to an endoscope having an insertion unit that is inserted into deep digestive tracts such as a small intestine and a large intestine to be observed.
2. Description of the Related Art
When an insertion unit of an endoscope is inserted in deep digestive tracts, such as a small intestine, since a force is not easily transmitted to a tip of the insertion unit by merely pushing the insertion unit because of complicated bending of an intestinal tract, it is hard to perform insertion into the depth. For example, when excessive bending or flexion arises in the insertion unit, it becomes impossible to further insert the insertion unit into the depth. Then, a method is proposed, which prevents excessive bending or flexion of an insertion unit by putting an insertion aid on the insertion unit of the endoscope and inserting the insertion unit into a body cavity, and guiding the insertion unit by this insertion aid.
Japanese Patent Application Laid-Open No. 2005-334475 discloses an endoscope apparatus which not only provides a first balloon in a tip portion of an insertion unit of an endoscope, but also provides a second balloon in a tip portion of an insertion aid (this is also called an over tube or a sliding tube). It is possible to make the insertion unit and insertion aid fix in an intestinal tract, such as a small intestine, by having the first balloon and second balloon expanded. Hence, by inserting the insertion unit and insertion aid by turns with repeating expansion and shrinkage of the first balloon and second balloon, it is possible to insert the insertion unit into the depth of a complicatedly bending intestinal tract, such as a small intestine.